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Prow

Prow is the system that handles GitHub events and commands for Kubernetes. It currently comprises several related pieces that live in a Kubernetes cluster. See the GoDoc for library docs. Please note that these libraries are intended for use by prow only, and we do not make any attempt to preserve backwards compatibility.

  • cmd/hook is the most important piece. It is a stateless server that listens for GitHub webhooks and dispatches them to the appropriate handlers.
  • cmd/plank is the controller that manages jobs running in k8s pods.
  • cmd/jenkins-operator is the controller that manages jobs running in Jenkins.
  • cmd/sinker cleans up old jobs and pods.
  • cmd/splice regularly schedules batch jobs.
  • cmd/deck presents a nice view of recent jobs.
  • cmd/phony sends fake webhooks.
  • cmd/tot vends incrementing build numbers.
  • cmd/horologium starts periodic jobs when necessary.
  • cmd/mkpj creates ProwJobs using Prow configuration.
  • cmd/mkpod creates Pods from ProwJobs.
  • cmd/clonerefs, cmd/initupload, cmd/gcsupload, cmd/entrypoint, and cmd/sidecar are small utilities used in ProwJobs created by plank as Pods. See their README for more information
  • cmd/tide manages merging PRs once they pass tests and match other criteria. See its README for more information.

See also: Life of a Prow Job

Getting started

See the doc here.

Contributing

Contributions in any form (issues, pull requests, even constructive comments in discussions) are more than welcome! If you work on a new feature or a change that impacts the default behavior of Prow, consider adding an announcement about it and dropping an email at the sig-testing mailing list.

How to test prow

Build with:

bazel build //prow/...

Test with:

bazel test --features=race //prow/...

TODO(spxtr): Unify and document how to run prow components locally.

How to run a given job on prow

Run the following, specifying JOB_NAME:

bazel run //prow/cmd/mkpj -- --job=JOB_NAME

This will print the ProwJob YAML to stdout. You may pipe it into kubectl. Depending on the job, you will need to specify more information such as PR number.

How to update the cluster

Any modifications to Go code will require redeploying the affected binaries. Fortunately, this should result in no downtime for the system. Run ./bump.sh <program-name> to bump the relevant version number in the makefile as well as in the cluster manifest, then run the image and deployment make targets on a branch which has the changes. For instance, if you bumped the hook version, run make hook-image && make hook-deployment.

Please ensure that your git tree is up to date before updating anything.

How to add new plugins

Add a new package under plugins with a method satisfying one of the handler types in plugins. In that package's init function, call plugins.Register*Handler(name, handler). Then, in hook/plugins.go, add an empty import so that your plugin is included. If you forget this step then a unit test will fail when you try to add it to plugins.yaml. Don't add a brand new plugin to the main kubernetes/kubernetes repo right away, start with somewhere smaller and make sure it is well-behaved.

The LGTM plugin is a good place to start if you're looking for an example plugin to mimic.

How to enable a plugin on a repo

Add an entry to plugins.yaml. If you misspell the name then a unit test will fail. If you have update-config plugin deployed then the config will be automatically updated once the PR is merged, else you will need to run make update-plugins. This does not require redeploying the binaries, and will take effect within a minute.

Note that Github events triggered by the account that is managing the plugins are ignored by some plugins. It is prudent to use a different bot account for performing merges or rerunning tests, whether the deployment that drives the second account is tide or the submit-queue munger.

How to add new jobs

To add a new job you'll need to add an entry into config.yaml. If you have update-config plugin deployed then the config will be automatically updated once the PR is merged, else you will need to run make update-config. This does not require redeploying any binaries, and will take effect within a minute.

Periodic config looks like so:

periodics:
- name: foo-job         # Names need not be unique.
  interval: 1h          # Anything that can be parsed by time.ParseDuration.
  agent: kubernetes     # See discussion.
  spec: {}              # Valid Kubernetes PodSpec.
  run_after_success: [] # List of periodics.

The agent should be "kubernetes", but if you are running a controller for a different job agent then you can fill that in here. The spec should be a valid Kubernetes PodSpec iff agent is "kubernetes".

Postsubmit config looks like so:

postsubmits:
  org/repo:
  - name: bar-job         # As for periodics.
    agent: kubernetes     # As for periodics.
    spec: {}              # As for periodics.
    max_concurrency: 10   # Run no more than this number concurrently.
    branches:             # Only run against these branches.
    - master
    skip_branches:        # Do not run against these branches.
    - release
    run_after_success: [] # List of postsubmits.

Postsubmits are run when a push event happens on a repo, hence they are configured per-repo. If no branches are specified, then they will run against every branch.

Presubmit config looks like so:

presubmits:
  org/repo:
  - name: qux-job            # As for periodics.
    always_run: true         # Run for every PR, or only when requested.
    run_if_changed: "qux/.*" # Regexp, only run on certain changed files.
    skip_report: true        # Whether to skip setting a status on GitHub.
    context: qux-job         # Status context. Usually the job name.
    max_concurrency: 10      # As for postsubmits.
    agent: kubernetes        # As for periodics.
    spec: {}                 # As for periodics.
    run_after_success: []    # As for periodics.
    branches: []             # As for postsubmits.
    skip_branches: []        # As for postsubmits.
    trigger: "(?m)qux test this( please)?" # Regexp, see discussion.
    rerun_command: "qux test this please"  # String, see discussion.

If you only want to run tests when specific files are touched, you can use run_if_changed. A useful pattern when adding new jobs is to start with always_run set to false and skip_report set to true. Test it out a few times by manually triggering, then switch always_run to true. Watch for a couple days, then switch skip_report to false.

The trigger is a regexp that matches the rerun_command. Users will be told to input the rerun_command when they want to rerun the job. Actually, anything that matches trigger will suffice. This is useful if you want to make one command that reruns all jobs.

Job Environment Variables

Prow will expose the following environment variables to your job. If the job runs on Kubernetes, the variables will be injected into every container in your pod, If the job is run in Jenkins, Prow will supply them as parameters to the build.

Variable Periodic Postsubmit Batch Presubmit Description Example
JOB_NAME ✓ ✓ ✓ ✓ Name of the job. pull-test-infra-bazel
JOB_TYPE ✓ ✓ ✓ ✓ Type of job. presubmit
JOB_SPEC ✓ ✓ ✓ ✓ JSON-encoded job specification. see below
BUILD_ID ✓ ✓ ✓ ✓ Unique build number for each run. 12345
PROW_JOB_ID ✓ ✓ ✓ ✓ Unique identifier for the owning Prow Job. 1ce07fa2-0831-11e8-b07e-0a58ac101036
BUILD_NUMBER ✓ ✓ ✓ ✓ Unique build number for each run. 12345
REPO_OWNER ✓ ✓ ✓ GitHub org that triggered the job. kubernetes
REPO_NAME ✓ ✓ ✓ GitHub repo that triggered the job. test-infra
PULL_BASE_REF ✓ ✓ ✓ Ref name of the base branch. master
PULL_BASE_SHA ✓ ✓ ✓ Git SHA of the base branch. 123abc
PULL_REFS ✓ ✓ ✓ All refs to test. master:123abc,5:qwe456
PULL_NUMBER ✓ Pull request number. 5
PULL_PULL_SHA ✓ Pull request head SHA. qwe456

Note: to not overwrite the Jenkins $BUILD_NUMBER variable, the build identifier will be passed as $buildId to Jenkins jobs.

Note: Use of $BUILD_NUMBER is deprecated. Please use $BUILD_ID instead.

Note: Examples of the JSON-encoded job specification follow for the different job types:

Periodic Job:

{"type":"periodic","job":"job-name","buildid":"0","prowjobid":"uuid","refs":{}}

Postsubmit Job:

{"type":"postsubmit","job":"job-name","buildid":"0","prowjobid":"uuid","refs":{"org":"org-name","repo":"repo-name","base_ref":"base-ref","base_sha":"base-sha"}}

Presubmit Job:

{"type":"presubmit","job":"job-name","buildid":"0","prowjobid":"uuid","refs":{"org":"org-name","repo":"repo-name","base_ref":"base-ref","base_sha":"base-sha","pulls":[{"number":1,"author":"author-name","sha":"pull-sha"}]}}

Batch Job:

{"type":"batch","job":"job-name","buildid":"0","prowjobid":"uuid","refs":{"org":"org-name","repo":"repo-name","base_ref":"base-ref","base_sha":"base-sha","pulls":[{"number":1,"author":"author-name","sha":"pull-sha"},{"number":2,"author":"other-author-name","sha":"second-pull-sha"}]}}

Bots home

@k8s-ci-robot and its silent counterpart @k8s-bot both live here as triggers to GitHub messages defined in config.yaml. Here is a command list for them.

Useful Talks

KubeCon 2018 EU

Automation and the Kubernetes Contributor Experience SIG Testing Deep Dive